package lab02.Test28;

/**
 * Created by 唐苗苗 on 2017/12/30.
 */
import java.util.Scanner;
public class Circle {
    public static void main(String[] args) {
        double a=0;
        System.out.println("输入半径：");
        Scanner scanner=new Scanner(System.in);
        a = scanner.nextDouble();
        System.out.println(a*a*3.14);
    }
}

